Yesterday, during OsmoDevCon 2018,
Steve Markgraf released osmo-fl2k,
a new Osmocom member project which enables the use of FL2000 USB-VGA adapters as
ultra-low-cost SDR transmitters.

How does it work?

A major part of any VGA card has always been a rather fast DAC which
generates the 8-bit analog values for (each) red, green and blue at the
pixel clock. Given that fast DACs were very rare/expensive (and still
are to some extent), the idea of (ab)using the VGA DAC to transmit radio
has been followed by many earlier, mostly proof-of-concept projects,
such as Tempest for Eliza in 2001.

However, with osmo-fl2k,
for the first time it was possible to completely disable the horizontal
and vertical blanking, resulting in a continuous stream of pixels
(samples). Furthermore, as the supported devices have no frame buffer
memory, the samples are streamed directly from host RAM.

As most USB-VGA adapters appear to have no low-pass filters on their DAC
outputs, it is possible to use any of the harmonics to transmit signals
at much higher frequencies than normally possible within the baseband of
the (max) 157 Mega-Samples per seconds that can be achieved.

osmo-fl2k and rtl-sdr

Steve is the creator of the earlier, complementary rtl-sdr software, which since
2012 transforms USB DVB adapters into general-purpose SDR receivers.

Today, six years later, it is hard to think of where SDR would be
without rtl-sdr. Reducing the entry cost of SDR receivers nearly down
to zero has done a lot for democratization of SDR technology.

There is hence a big chance that his osmo-fl2k project will attain a
similar popularity. Having a SDR transmitter for as little as USD 5 is
an amazing proposition.

free riders

Please keep in mind that Steve has done rtl-sdr just for fun, to scratch
his own itch and for the "hack value". He chose to share his work with
the wider public, in source code, under a free software license. He's
a very humble person, he doesn't need to stand in the limelight.

Many other people since have built a business around rtl-sdr. They have
grabbed domains with his project name, etc. They are now earning money
based on what he has done and shared selflessly, without ever
contributing back to the pioneering developers who brought this to all
of us in the first place.

So, do we want to bet if history repeats itself? How long will it take
for vendors showing up online advertising the USB VGA dongles as "SDR
transmitter", possibly even with a surcharge? How long will it take for
them to include Steve's software without giving proper attribution? How
long until they will violate the GNU GPL by not providing the complete
corresponding source code to derivative versions they create?

If you want to thank Steve for his amazing work

reach out to him personally

contribute to his work, e.g.

help to maintain it

package it for distributions

send patches (via osmocom-sdr mailing list)

register an osmocom.org account and update the wiki with more information

And last, but not least, carry on the spirit of "hack value" and
democratization of software defined radio.

Thank you, Steve! After rtl-sdr and osmo-fl2k,
it's hard to guess what will come next :)